Werkhoven P. & Groen J. (1998), Manipulation performance in interactive virtual environments, Human Factors. Vol. 40 Nr. 3, 432-442. We have studied manipulation performance in virtual environments using two types of controlers: virtual hand control and 3D mouse/cursors control. These manipulation methods were tested under monoscopic and stereoscopic viewing conditions. Participants were asked to discriminate, grasp, pitch, roll and position virtual objects. Both speed and accuracy of manipulation tasks were measured. Virtual hand control proved to be significantly faster and more accurate than 3D mouse cursor control. Virtual hand control affected more head movement which was available in both conditions. Further, it was shown that the speed and accuracy of manipulations strongly improve under stereoscopic viewing conditions.
Groen J. & Werkhoven P. (1998). Visuo-motor adaptation to virtual hand position in interactive virtual environments. Presence, Vol. 7, Nr. 5, 429-446. In virtual environments the virtual hand may not always be exactly aligned with the real hand. Such misalignment may cause an adaptation of the users’ eye-hand coordination. Further, misalignment may cause a decrease in manipulation performance compared to aligned condi¬tions. This experimental study uses a prism adaptation paradigm to explore visuo-motor adapta¬tion to misaligned virtual hand position. Participants were immersed in an interactive virtual environment with a deliberately misaligned virtual hand position (a lateral shift of 10 cm). We carried out pointing tests with a non-visible hand in the real world before (pre-test) and after (post-test) immersion in the virtual world. A comparison of pre- and post-tests revealed after-effects of the adaptation of eye-hand coordina¬tion in the opposite direction of the lateral shift (negative after-effects). The magnitude of the after-effect was 20% under stereoscopic viewing conditions. However, decreased manipulation performance in VE (speed/ accuracy) during the immersion with misaligned hand conditions was not found.
Bakker N.H., Werkhoven P.J. & Passenier P.O. (1999). The effects of proprioceptive and visual feedback on geographical orientation in virtual environments. Presence. 8 (1), 36-53. To effectively use a virtual environment (VE) for applications such as training and design evaluation, a good sense of orientation is needed in the VE. ‘‘Natural’’ human geographical orientation, when moving around in the world, relies on visual as well as proprioceptive feedback. However, the present navigation metaphors that are used to move around in the VE often lack proprioceptive feedback. To investigate the possible consequences this may have, an experiment was conducted on the relative contributions of visual and proprioceptive feedback on path integration in VE. Subjects were immersed in a virtual forest and were asked to turn speci.c angles under different combinations of visual, vestibular, and kinesthetic feedback (pure visual, visual plus vestibular, visual plus vestibular plus kinesthetic, pure vestibular, and vestibular plus kinesthetic). Furthermore, two visual conditions with different visual flows were tested: normal visual flow and decreased visual flow provided by a 60% zoom. Results show that kinesthetic feedback provides the most reliable and accurate source of information to use for path integration, indicating the bene.ts of incorporating this kind of feedback in navigation metaphors. Orientation based on visual flow alone is most inaccurate and unreliable. In all conditions, subjects overestimated their turning speed and subsequently didn’t turn far enough. Both the absolute errors and the variation in path integration increase with the length of the path.
Bakker N.H., Werkhoven P.J. & Passenier P.O. (2001). Calibrating Visual Path Integration in VE. Presence 10 (2), 216-224. When moving around in the world, humans can use the motion sensations provided by their kinesthetic, vestibular, and visual senses to maintain their sense of direction. Previous research in virtual environments (VEs) has shown that this socalled path integration process is inaccurate in the case that only visual motion stimuli are present, which may lead to disorientation. In an experiment, we investigated whether participants can calibrate this visual path integration process for rotations; in other words, can they learn the relation between visual flow and the angle that they traverse in the VE? Results show that, by providing participants with knowledge of results (KR), they can indeed calibrate the biases in their path integration process, and also maintain their improved level of performance on a retention test the next day.
Bakker, N.H., Passenier, P.O, & Werkhoven, P.J. (2003). The Effects of Head-Slaved Navigation and the use of Teleports on Spatial Orientation in Virtual Environments (VE). Human Factors, 45(1), 160-169. The type of navigation interface in a VE, head--slaved or indirect, determines whether proprioceptive feedback stimuli are present or not during movement. Besides continuous movement, teleports can be used, which discontinuously displace the viewpoint over large distances. An experiment was performed consisting of two parts. The first part investigated whether head--slaved navigation provides an advantage for spatial learning in a VE. The second part investigated the role of anticipation when using teleports. The results showed that head--slaved navigation has an advantage over indirect navigation for the acquisition of spatial knowledge in a VE. Anticipation to the destination of the teleport prevented disorientation after the displacement to a great extent but not completely. The time that was needed for anticipation increased if the teleport involved a rotation of the viewing direction.